Thermosetting resins are an important part of the pultrusion of composite parts. In the most basic sense: thermosetting resins are liquefied polymers that harden irreversibly by curing. The introduction of thermal energy, ultraviolet (UV) or radio frequency (RF) waves causes cross-linking of individual polymer chains within the resin, resulting in a polymer network that is neither soluble nor soluble.

Crosslinking is characterized by the formation of covalent bonds between different polymer chains in the thermosetting resin. This depends on a number of factors, including the nature and distribution of the monomers throughout the resin and the unique crosslinking mechanism. Fortunately, the various acrylic resins, epoxies, phenolics and other thermoset resins used in pultrusion have been characterized in sufficient detail to ensure uniformity of the polymer network in the cured composite part.

How to use thermosetting resin?

Fiber reinforced composite (FRP) materials are manufactured by impregnating glass reinforced textiles with high performance thermosetting resins and curing the composite after the formation stage.

In a typical pultrusion process: the mat creel positions the textile in a position that can be fed into the reinforced guide. The fabric was then pulled through a resin bath and “wet” treatment was carried out in a resin bath. The bath contains a thermosetting resin, as well as any other fillers, pigments or catalysts required to accelerate cross-linking during the curing stage. The resin mixture completely saturates the fabric before passing through the shrink preformer. This is necessary to optimally position and organize the near net shape reinforcement while removing any excess liquid from the impregnator before the impregnator passes through the curing mold.

Crosslinking begins when the thermosetting resin is typically thermally activated by electrical induction or by a radio frequency (RF) wave generator. The energy provided by these instruments cures the thermosetting resin with the reinforcing elements embedded therein. It is then cooled and cut to the appropriate length.

Why use thermosetting resins?

Thermosetting resins are primarily used to impart structural and thermal stability to composite parts, but standard resin systems can be readily modified to achieve the desired characteristics. Although pultruded polymer composites are not easily melted, they may still deform or burn at high temperatures. Various phenolic resins are used to increase the temperature resistance of polymer composites and improve their fire resistance to meet demanding applications. Different thermosetting resins are specified depending on the application area of the custom component and the customer specifications.